CIE Mar 2016 v2 Paper 4 Q4

Answers available below

PMT (a) Ethanal, CH3CHO, dimerises in alkaline solution according to the following equation. 2CH3CHOCH3CH(OH)CH2CHO The initial rate of this reaction was measured, starting with different concentrations of CH3CHO and OH. The following results were obtained. [CH3CHO] / mol dm3 [OH] / mol dm3 initial rate of reaction (relative values) 0.10 0.20 0.40 0.015 0.015 0.030 1 2 8 (i) Deduce the order of the reaction with respect to CH3CHO.[1] (ii) Deduce the order of the reaction with respect to OH.[1] (iii) State the overall rate equation for this reaction. rate =[1] (iv) State the units for the rate constant, k.[1] (v) Calculate the initial rate of reaction (relative value) for a reaction where the [CH3CHO] is 0.30 mol dm3 and [OH] is 0.030 mol dm3. [1]UCLES 2016 9701/42/F/M/16<br />
 PMT (b) (i) A three-step mechanism has been proposed for the reaction in (a). step 1 CH3 step 2 CH3 OH CH2 CH2 CH3 H2O O CH2 step 3 CH3 O CH2 H2O CH3 OH CH2 OH Using your rate equation in (iii), predict which is the rate-determining step. Explain your answer. rate-determining stepexplanation[2] (ii) Describe the chemical behaviour of CH3CHO in step 1.[1] (c) Name the mechanism occurring in steps 2 and 3.[1] (d) Using the diagram below, show the mechanism for step 2 showing the relevant curly arrows and dipoles. CH3 CH2UCLES 2016 9701/42/F/M/16 [2] [Total: 11] [Turn over<br />

Show answer